JP2007170534A - Gas bearing spindle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an easily manufacturable gas bearing spindle capable of damping rotary run-out vibration of a rotary shaft efficiently. <P>SOLUTION: This gas bearing spindle 1 is provided with the rotary shaft 10, a sleeve 30 having a cylindrical sleeve through hole 33 surrounding a part of an outer peripheral face 11A of the rotary shaft 10, and a housing 20 surrounding the sleeve 30 and holding the sleeve 30 through rubber-made O rings 41, 42. The sleeve 30 includes a bearing part 31 made of a non-metallic sintered body constituted to have the sleeve through hole 33, form an outer peripheral face of the sleeve 30 by a part of its outer peripheral face, and let an inner peripheral face of the sleeve through hole 33 oppose to the outer peripheral face of the rotary shaft 10 and metallic holding rings 32 fitted into each of end parts on both sides of the bearing part 31 in the direction in which the sleeve through hole 33 is extended and holding the sleeve 30 for the housing 20 through the O rings 41, 42. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a gas bearing spindle, and more particularly to a gas bearing spindle used in precision processing machines, hole processing machines, electrostatic coating machines, and the like.

  A gas bearing spindle having a gas bearing in which a rotating shaft is supported with respect to the housing by supplying a gas such as compressed air to a minute gap between the rotating shaft and a member facing the rotating shaft inside the housing. The rotary shaft is supported in a non-contact state with respect to the housing. Therefore, not only the friction loss in the bearing is small, but also the rotating shaft and the member facing the rotating shaft are not in direct contact, so that the member is not fatigued or worn as long as it is in a normal operating state. Taking advantage of such features, gas bearing spindles are widely used as high-speed spindles used in precision processing machines, hole processing machines, electrostatic coating machines and the like.

  Various proposals have been made for this gas bearing spindle in order to improve its performance. For example, a gas bearing that employs a sleeve having an inner wall made of graphite as a member facing the rotating shaft in order to avoid seizure of the rotating shaft even if the rotating shaft and a member facing the rotating shaft contact each other. A spindle has been proposed. In addition, there is a case where a gas bearing spindle capable of absorbing a whirling vibration of the rotating shaft by supporting a sleeve as a member opposed to the rotating shaft with respect to the housing via an O-ring (for example, patent) Reference 1).

  FIG. 3 is a schematic partial sectional view showing an example of a conventional gas bearing spindle. An example of a conventional gas bearing spindle will be described with reference to FIG.

  Referring to FIG. 3, a conventional gas bearing spindle 100 includes a rotating shaft 110, a bearing sleeve 130 that surrounds a part of the outer peripheral surface of the rotating shaft 110 with a bearing gap 150 therebetween, and a housing 120 that surrounds the bearing sleeve 130. It has. The bearing sleeve 130 is supported with respect to the housing 120 via rubber O-rings 141 and 142. The bearing sleeve 130 includes an inner cylinder member 131 made of a sintered material such as graphite and an outer cylinder member 132 made of metal. The outer cylinder member 132 is fitted to the outer peripheral surface of the inner cylinder member 131 with a predetermined tightening allowance by shrink fitting. Further, nozzles 160 are formed in the vicinity of both ends of the bearing sleeve 130. The nozzle 160 is connected to a bearing gas supply unit (not shown) via a sleeve air supply path 161, an annular space 170 closed by the bearing sleeve 130, the housing 120 and the O-ring 142, and an air supply path 180. .

  Next, the operation of the conventional gas bearing spindle 100 will be described. By supplying high-pressure gas supplied from a bearing gas supply unit (not shown) to the bearing gap 150 via the air supply passage 180, the annular space 170, the sleeve air supply passage 161 and the nozzle 160, the rotary shaft 110 is made to have a bearing sleeve. It is supported in a non-contact manner so as to be rotatable with respect to 130. The rotating shaft 110 rotates in the circumferential direction of the rotating shaft 110 by being given a driving force by driving means (not shown).

At this time, since the bearing sleeve 130 has the inner cylindrical member 131 made of a sintered material such as graphite, even if the rotating shaft 110 and the bearing sleeve 130 come into contact with each other, the rotating shaft 110 is seized. Can be suppressed. Further, since the bearing sleeve 130 is supported with respect to the housing 120 via the O-rings 141 and 142, the whirling vibration of the rotating shaft 110 can be damped.
JP 2002-295470 A

  As described above, according to the gas bearing spindle 100 shown in FIG. 3, the whirling vibration of the rotating shaft 110 can be damped using the elasticity of the O-rings 141 and 142. However, when the mass of the bearing sleeve 130 increases, the natural frequency of the entire system supported by the O-rings 141 and 142 decreases, and the response of the bearing sleeve to the whirling vibration of the rotating shaft 110 decreases. As a result, the effect of attenuating the whirling vibration of the rotating shaft 110 by the O-rings 141 and 142 is reduced.

  As shown in FIG. 3, when the bearing sleeve 130 has a two-layer structure in which the graphite inner cylinder member 131 is surrounded by a metal outer cylinder member 132 having a large mass, the mass of the bearing sleeve 130 increases, as described above. In addition, the effect of attenuating the whirling vibration of the rotating shaft 110 by the O-rings 141 and 142 is reduced.

  On the other hand, the bearing sleeve 130 can be reduced in weight by making the entire bearing sleeve 130 made of a sintered material such as graphite. However, since the sintered material is more fragile than metal, when assembling the gas bearing spindle 100 or the like, when the bearing sleeve 130 is inserted into or removed from the housing 120, the bearing sleeve 130 may be damaged due to an unexpected impact or the like. There is a problem that damage is likely to occur.

  Further, the inner peripheral surface of the bearing sleeve 130 needs to be processed with extremely high precision in order to form a minute bearing gap 150. In general, the processing is performed after the bearing sleeve 130 is firmly fixed by holding a part of the bearing sleeve 130. However, since the sintered material is more fragile than the metal, damage is likely to occur in the portion where the bearing sleeve 130 is held, as described above. Furthermore, since the sintered material generally has a small longitudinal elastic modulus, the held portion is likely to be deformed, and it is difficult to stably fix it, and it is difficult to realize high-precision processing. Therefore, in order to realize highly accurate processing, processing including complicated processes is required, which causes an increase in manufacturing cost.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a gas bearing spindle that can efficiently attenuate the whirling vibration of a rotating shaft and is easy to manufacture.

  A gas bearing spindle according to the present invention includes a rotary shaft, a sleeve having a sleeve through hole which is a cylindrical through hole surrounding at least a part of the outer peripheral surface of the rotary shaft, a sleeve surrounding the sleeve, and an elastic member interposed between the sleeve And a housing for holding. The sleeve has a sleeve through hole, a part of the outer peripheral surface forms the outer peripheral surface of the sleeve, and the inner peripheral surface of the sleeve through hole faces the outer peripheral surface of the rotating shaft. And a metal holding ring that is fitted to each of both end portions of the bearing portion in the extending direction of the sleeve through hole and holds the sleeve against the housing via an elastic member.

  According to the gas bearing spindle of the present invention, the sleeve is basically not a two-layer structure of a graphite inner cylinder member and a metal outer cylinder member. It is constituted by. As a result, the weight of the sleeve is reduced, the natural frequency of the entire system including the sleeve supported by the elastic member is increased, and the response to the whirling vibration of the rotating shaft is improved. As a result, it is possible to improve the effect of attenuating the vibration around the rotating shaft caused by the elastic member. Furthermore, in the gas bearing spindle of the present invention, a metal holding ring is fitted into the end of the bearing that is the end of the sleeve. For this reason, when the sleeve is inserted into and removed from the housing, damage to the sleeve can be suppressed by protecting both end portions of the sleeve, which are likely to be chipped by an impact due to accidental contact, with a metal retaining ring. In addition, when processing the inner peripheral surface of the sleeve, the sleeve is damaged by holding the sleeve so that stress is applied to the metal holding ring having higher toughness than the non-metallic sintered body. This can be suppressed.

  Furthermore, when processing the inner peripheral surface of the sleeve, it is easy to firmly fix the sleeve by holding the sleeve so that stress is applied to the metal holding ring having a larger longitudinal elastic modulus than the sintered material. High-precision machining can be easily realized.

  As described above, according to the gas bearing spindle of the present invention, it is possible to provide a gas bearing spindle that can efficiently attenuate the whirling vibration of the rotating shaft and is easy to manufacture.

  Here, as the nonmetal sintered body constituting the bearing portion of the sleeve, for example, graphite or ceramic formed by sintering can be employed. Further, from the viewpoint of reducing the weight of the sleeve, the specific gravity of the nonmetallic sintered body constituting the bearing portion of the sleeve is preferably small. For example, it is more effective to employ a nonmetallic sintered body having a specific gravity of 5 or less. .

  Further, from the viewpoint of reducing the weight of the sleeve, it is preferable that the length of the holding ring in the direction in which the sleeve through hole extends is short and the thickness is small. Specifically, the length of the retaining ring is preferably 30% or less of the length of the sleeve in the direction in which the sleeve through-hole extends, for example. On the other hand, when the sleeve is inserted into and removed from the housing or when the inner peripheral surface of the sleeve is processed, the retaining ring has a certain length and thickness in order to sufficiently function as a portion held by another member. It is preferable to have. Specifically, the length of the retaining ring is preferably 5% or more of the length of the sleeve in the direction in which the sleeve through hole extends, and the thickness is preferably 20% or more of the thickness of the sleeve. As the above-mentioned elastic member, for example, nitrile rubber, fluororubber, silicone rubber or the like can be employed.

  Moreover, as a metal which comprises a retaining ring, an iron-type alloy, an aluminum-type alloy, a magnesium-type alloy etc. can be employ | adopted, Specifically, for example, JIS specification SUS304, SUS303 (stainless steel), A2000 type (aluminum) Based alloys) or the like.

  Preferably, in the gas bearing spindle, the holding ring is formed with an annular groove extending in the direction along the outer periphery of the holding ring for holding the elastic member.

  Thereby, for example, a rubber O-ring is employed as the elastic member, and the position of the O-ring can be fixed by fitting the O-ring into the annular groove. Moreover, if the groove | channel for fixing an elastic member is formed in the bearing part which consists of a non-metallic sintered body which is weak compared with a metal, a process will become difficult. In addition, it is difficult to process with high surface accuracy, and depending on the contact portion between the non-metallic sintered body having pores inside and the elastic member, there is a possibility that sufficient airtightness may not be secured. Therefore, this configuration is not suitable for a gas bearing spindle that needs to ensure airtightness. On the other hand, by forming the annular groove in the metal holding ring that is less likely to have pores inside and relatively easy to process with high surface accuracy, the groove can be easily processed. At the same time, the airtightness can be sufficiently secured by the contact portion between the metal holding ring and the elastic member.

  Preferably, in the above gas bearing spindle, the sleeve is formed with a plurality of nozzles for supplying gas to a bearing gap provided between the inner peripheral surface of the sleeve through hole and the outer peripheral surface of the rotary shaft on the peripheral wall of the sleeve. Has been. And the nozzle is arrange | positioned so that the some line | wire extended in the circumferential direction of a sleeve through-hole may be comprised.

  The rotating shaft is held out of contact with the sleeve by the pressure in the bearing gap caused by bearing gas such as compressed air supplied through the nozzle. Therefore, by forming a plurality of the nozzles and arranging the nozzles so as to form a plurality of rows, the rigidity of the gas bearing can be increased and higher bearing performance can be obtained.

  Preferably, in the gas bearing spindle, at least one row of nozzles is formed on each of both sides sandwiching the central portion of the sleeve in the direction in which the sleeve through hole extends. Thereby, it is possible to make a gas bearing spindle having high angular rigidity with respect to the inclination of the rotating shaft.

  Preferably, in the gas bearing spindle, the end nozzles located at both ends of the plurality of nozzles in the direction in which the sleeve through-hole extends are such that the distance from one end closest to both ends of the sleeve is the distance of the sleeve. It is formed at a position that is 25% or less of the length. In order for the bearing to have high angular rigidity with respect to the inclination of the rotating shaft, it is preferable that a bearing nozzle for supplying bearing gas is provided at a position separated by a predetermined distance or more. With the above-described configuration, the journal bearing can have high angular rigidity with respect to the inclination of the rotating shaft.

  Preferably, in the gas bearing spindle, at least one nozzle is formed at a position where the distance from the central portion of the sleeve is 20% or less of the length of the sleeve in the extending direction of the sleeve through hole.

  In the gas bearing spindle in which the sleeve is held in the housing through the elastic member like the gas bearing spindle of the present invention, the heat conductivity between the sleeve and the housing is low. Easy to collect. When the rotating shaft rotates at a high speed for a long time, the gas in the bearing gap generates heat due to friction, resulting in an increase in the temperature around the bearing gap. There is a risk of contact between the rotating shaft and the sleeve due to the reduction.

  On the other hand, as described above, since the nozzle is formed in the vicinity of the center of the sleeve, the pressure of the bearing clearance facing the vicinity of the center of the sleeve is higher than that in the surrounding bearing clearance. For this reason, an air flow is generated from the area facing the center of the sleeve between the bearing gaps to the area facing the end of the sleeve, and the increased temperature of the bearing gas existing in the bearing gap effectively increases the end of the sleeve. It is discharged toward the area facing the surface, and the rise in temperature is mitigated. As a result, the malfunction of the gas bearing spindle due to the above-described thermal expansion can be avoided.

  As is apparent from the above description, according to the gas bearing spindle of the present invention, it is possible to provide a gas bearing spindle that can efficiently attenuate the whirling vibration of the rotating shaft and is easy to manufacture. .

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following drawings, the same or corresponding parts are denoted by the same reference numerals, and the description thereof will not be repeated.

(Embodiment 1)
FIG. 1 is a schematic cross-sectional view of a gas bearing spindle according to Embodiment 1, which is an embodiment of the present invention. With reference to FIG. 1, the structure of the gas bearing spindle in Embodiment 1 of this invention is demonstrated.

  Referring to FIG. 1, a gas bearing spindle 1 according to Embodiment 1 includes a rotary shaft 10 and a sleeve 30 having a sleeve through hole 33 that is a cylindrical through hole surrounding a part of the outer peripheral surface 11 </ b> A of the rotary shaft 10. And a housing 20 that surrounds the sleeve 30 and holds the sleeve 30 via rubber O-rings 41 and 42 as elastic members. The rotary shaft 10 and the sleeve 30 are arranged with a journal bearing gap 13 of about 10 μm or more and 40 μm or less separated.

  The rotating shaft 10 includes a cylindrical shaft portion 11 and a flange portion 12 having a disk shape having a diameter larger than that of the shaft portion 11 formed at one end of the shaft portion 11. A holding part 19 for holding a tool or the like is formed at the other end of the part 11. In the sleeve 30, bearing gas is formed in a journal bearing gap 13 formed on the peripheral wall of the sleeve 30 and provided between the inner peripheral surface of the sleeve through-hole 33 and the outer peripheral surface 11 A of the shaft portion 11 of the rotary shaft 10. A journal nozzle 51, which is a plurality of nozzles for supplying the ink, is formed.

  The journal nozzles 51 are arranged so as to form two rows extending in the circumferential direction of the sleeve through-holes 33, and the journal nozzles 51 are arranged in the direction in which the sleeve through-holes 33 extend (the shaft in the shaft portion 11 of the rotary shaft 10. 1 row in each direction across the central portion of the sleeve 30 in the direction).

  With the above configuration, the sleeve 30 functions as a gas journal bearing that supports the rotating shaft 10 with respect to the housing 20 in a non-contact manner in a direction perpendicular to the axial direction of the shaft portion 11 (radial direction). The journal nozzle 51 is preferably formed so that the distances from the central portion of the sleeve 30 to the journal nozzles 51 on both sides in the axial direction of the shaft portion 11 are substantially equal. As a result, the pressure distribution in the journal bearing gap 13 is substantially symmetrical in the axial direction, and the rotary shaft 10 is pivotally supported with respect to the sleeve 30 in a balanced manner in the axial direction.

  Further, a gas thrust bearing 60 having an annular shape is disposed inside the housing 20 such that one bottom surface faces each of the bottom surfaces 12A on both sides of the flange portion 12 of the rotating shaft 10. . Here, the gas thrust bearing 60 and the flange portion 12 of the rotary shaft 10 are disposed with a thrust bearing gap 14 of about 10 μm to 50 μm. The gas thrust bearing 60 is formed with a plurality of thrust nozzles 61 for supplying gas to the thrust bearing gap 14 provided between the one bottom surface and the bottom surface 12A of the flange portion 12 facing the one bottom surface. ing. A plurality of thrust nozzles 61 are formed in a direction along the circumferential direction of the flange portion 12.

  Further, the journal nozzle 51 has a bearing gas supply path 21 formed in the housing 20 through a sleeve air supply path 52 and an annular space 22 which is a space closed by the sleeve 30, the housing 20 and the O-ring 42. It is connected to the. The thrust nozzle 61 is connected to the bearing gas supply path 21 via a thrust bearing supply path 62. The bearing gas supply path 21 has a function of supplying a high-pressure gas such as air, and is connected to a bearing gas supply source such as an air compressor (not shown) disposed outside the gas bearing spindle 1. .

  Furthermore, a thin portion 12B having a smaller axial thickness than an adjacent portion in the flange portion 12 is formed on the outer peripheral portion which is a part of the flange portion 12, and on one bottom surface of the thin portion 12B, A plurality of turbine blades 15 are formed that are arranged in the circumferential direction of the flange portion 12, have a plate-like shape, and receive the blown gas to rotate the rotating shaft 10 in the circumferential direction of the flange portion 12. Yes. Further, the housing 20 is disposed on the outer peripheral side of the flange portion 12, has an opening at a position facing the turbine blade 15, and a driving gas such as compressed air from the inner wall of the housing 20 toward the turbine blade 15. A turbine nozzle 73 is formed so as to be able to eject the gas. The turbine nozzle 73 is connected to a driving gas supply path 71 via a circumferential groove 72 formed so as to extend in a direction along the outer periphery of the flange portion 12. The driving gas supply path 71 has a function of supplying a gas such as high-pressure air, and is connected to a driving gas supply source such as an air compressor (not shown) disposed outside the gas bearing spindle 1. . Further, the housing 20 has a surface on the side where the turbine blades 15 of the thin portion 12B of the flange portion 12 are formed, and is opposed to a region on the inner peripheral side of the region where the turbine blades 15 are formed. A driving gas discharge path 75 having the other opening is formed on the outer wall of the housing 20.

  Next, the operation of the gas bearing spindle 1 of the first embodiment will be described with reference to FIG. Bearing gas such as compressed air supplied from a bearing gas supply source (not shown) is supplied to the journal bearing gap 13 through the bearing gas supply path 21, the sleeve air supply path 52, and the journal nozzle 51. Further, the bearing gas supplied from a bearing gas supply source (not shown) is supplied to the thrust bearing gap 14 through the bearing gas supply path 21, the thrust bearing supply path 62 and the thrust nozzle 61. Thereby, in the journal bearing gap 13 and the thrust bearing gap 14, a gas film is formed by the supplied bearing gas. As a result, the rotating shaft 10 is supported in a non-contact and rotatable manner with respect to the housing 20 in a direction (radial direction) and an axial direction (axial direction) perpendicular to the axial direction of the rotating shaft 10.

  Further, the driving gas supplied from a driving gas supply source such as an air compressor (not shown) is supplied from the driving gas supply path 71 to the turbine nozzle 73 through the circumferential groove 72. The driving gas supplied to the turbine nozzle 73 is ejected toward the turbine blade 15. When the jetting driving gas is received by the turbine blade 15, a driving force (torque) that rotates around the axis of the rotating shaft 10 is applied to the flange portion 12, and the rotating shaft 10 rotates around the axis. The driving gas that gives the driving force to the rotating shaft 10 is discharged from the driving gas discharge path 75 to the outside of the gas bearing spindle 1.

  Here, the sleeve 30 has a sleeve through hole 33, a part of the outer peripheral surface forms the outer peripheral surface of the sleeve 30, and the inner peripheral surface of the sleeve through hole 33 faces the outer peripheral surface 11 </ b> A of the rotary shaft 10. The bearing portion 31 made of a non-metallic sintered body configured in the above-described manner and the end portions on both sides of the bearing portion 31 in the extending direction of the sleeve through-hole 33 (the axial direction of the rotary shaft 10) are fitted into each other. And a metal holding ring 32 that holds the sleeve 30 against the housing 20 via rubber O-rings 41 and 42 that are elastic members. The retaining ring 32 can be fitted into the bearing portion 31 by, for example, shrink fitting.

  As described above, in the gas bearing spindle 1 of the first embodiment, the sleeve 30 is basically composed of a non-metallic sintered body having a small specific gravity. As a result, the sleeve 30 is reduced in weight, the natural frequency of the entire system including the sleeve 30 supported by the rubber O-rings 41 and 42 as elastic members is increased, and the whirling vibration of the rotary shaft 10 is increased. Responsiveness to is improved. As a result, the whirling vibration of the rotating shaft 10 can be effectively damped by the deformation of the O-rings 41 and 42. Furthermore, in the gas bearing spindle 1 according to the first embodiment, a metal holding ring 32 is fitted on the end of the bearing 31 that is the end of the sleeve 30. Therefore, when the sleeve 30 is inserted into and removed from the housing 20 or when the inner peripheral surface of the sleeve 30 is processed, stress is applied to the metal retaining ring 32 having higher toughness than the non-metallic sintered body. By holding the sleeve 30 as described above, it is possible to prevent the sleeve 30 from being damaged. Moreover, damage to the sleeve can be suppressed by protecting both end portions of the sleeve, which are likely to be chipped by an impact due to accidental contact, with a metal retaining ring.

  Further, when the inner peripheral surface of the sleeve 30 is processed, the sleeve 30 is held so that stress is applied to the metal holding ring 32 having a larger longitudinal elastic coefficient than that of the sintered material. And high-precision machining can be easily realized.

  As described above, according to the gas bearing spindle 1 of the first embodiment, it is possible to provide a gas bearing spindle that can efficiently attenuate the whirling vibration of the rotating shaft and can be easily manufactured.

  Furthermore, in the gas bearing spindle 1 of the first embodiment, the holding ring 32 is formed with an annular groove 32A extending in the direction along the outer periphery of the holding ring 32 for holding the O-rings 41 and 42. . The positions of the O-rings 41 and 42 are fixed by being fitted into the grooves 32A.

  Thereby, the positions of the O-rings 41 and 42 can be stably fixed. In addition, by forming a groove in a metal holding ring 32 that is easy to process with high surface accuracy compared to a non-metal sintered body and has a small possibility of having pores inside, O-rings 41 and 42, The airtightness of the annular space 22 can be sufficiently secured. In addition, since the metal retaining ring 32 is less likely to be chipped or cracked than a non-metallic sintered body, it can be easily processed into a complicated shape having a thin portion.

  Further, in the gas bearing spindle 1 of the first embodiment, the end nozzles (journal nozzles) 51 located at both ends of the plurality of journal nozzles 51 in the extending direction of the sleeve through-hole 33 are the ends on both sides of the sleeve 30. It is preferable that the distance from the closest end of the portions is 25% or less of the length of the sleeve 30. Thereby, the journal bearing can have high angular rigidity with respect to the inclination of the rotating shaft. Here, in the end nozzle 51, the center of the opening on the side facing the rotation axis 10 of the end nozzle 51 (for example, the center is the center if the opening is circular, and the midpoint between the two focal points is the ellipse). If it is arrange | positioned in this position, the conditions regarding the position of the said edge part nozzle 51 are satisfy | filled.

  The holding ring 32 is preferably made of a metal having a large longitudinal elastic modulus, such as stainless steel, steel, aluminum, aluminum alloy, or the like. Accordingly, when the sleeve 30 is processed, the sleeve 30 is fixed by holding the holding ring 32, whereby deformation of the holding ring 32 is suppressed, and the sleeve 30 can be processed with higher accuracy. .

  Further, when the rotary shaft 10 rotates at a high speed, heat generation due to bearing loss increases and the sleeve 30 expands thermally. In this case, the inner diameter of the sleeve through-hole 33 is increased at both ends of the sleeve 30 in which the metal holding ring 32 having a larger linear expansion coefficient than that of the nonmetal sintered body is fitted. However, by setting the journal bearing gap 13 to an appropriate size, the influence on the bearing performance due to the change in the inner diameter of the sleeve through hole 33 can be avoided. Further, by adopting a material having a small linear expansion coefficient, such as an invar material (alloy of 36% nickel and 64% iron), as the material of the holding ring 32, a change in the inner diameter of the sleeve through hole 33 at both ends of the sleeve 30 is suppressed. Then, the influence on the bearing performance due to the change in the inner diameter of the sleeve through hole 33 may be avoided.

  Further, as the material of the rotating shaft 10, a relatively inexpensive steel-based metal material can be employed. In order to improve corrosion resistance and wear resistance, the surface of the rotating shaft 10 may be subjected to a surface treatment such as a plating treatment such as hard chrome plating. Further, as the material of the rotating shaft 10, an invar material, ceramic, or the like having a smaller linear expansion coefficient than that of a steel metal material may be employed. When the rotating shaft 10 rotates at a high speed, heat generation due to bearing loss increases, and the outer diameter of the rotating shaft 10 increases. As a result, the journal bearing gap 13 becomes narrow, which may affect the bearing performance. On the other hand, by adopting a material having a small linear expansion coefficient, such as Invar material or ceramic, as the material of the rotating shaft 10, it is possible to suppress the change in the outer diameter of the rotating shaft 10 and to suppress the influence on the bearing performance. it can.

(Embodiment 2)
FIG. 2 is a schematic cross-sectional view of the gas bearing spindle according to the second embodiment which is an embodiment of the present invention. With reference to FIG. 2, the structure of the gas bearing spindle in Embodiment 2 of this invention is demonstrated.

  Referring to FIG. 2, the gas bearing spindle 1 of the second embodiment basically has the same configuration as the gas bearing spindle 1 of the first embodiment, and has the same effect. However, the gas bearing spindle 1 according to the second embodiment is different from the gas bearing spindle 1 according to the first embodiment in that a central journal nozzle 51C is formed in the central portion of the sleeve 30 in the axial direction.

  The central journal nozzle 51 </ b> C is formed at a position where the distance from the central portion of the sleeve 30 is 20% or less of the length of the sleeve 30 in the direction in which the sleeve through-hole 33 extends. Here, the center journal nozzle 51C has the center of the opening on the side facing the rotation axis 10 of the center journal nozzle 51C (for example, the center is the center if the opening is circular, and the middle point between the two focal points if the opening is circular). If it is disposed at the position, the condition regarding the position of the central journal nozzle 51C is satisfied.

  When the rotary shaft 10 rotates at a high speed for a long time, the gas in the journal bearing gap 13 generates heat due to friction, whereby the temperature around the journal bearing gap 13 rises and the journal bearing gap 13 becomes smaller. There is a risk that problems such as contact between the shaft 10 and the sleeve 30 may occur. On the other hand, since the central journal nozzle 51C is formed as described above, the air pressure in the journal bearing gap 13 facing the vicinity of the center of the sleeve 30 becomes higher than the surroundings. Therefore, an airflow is generated from the region facing the center of the sleeve 30 in the journal bearing gap 13 toward the region facing the end of the sleeve 30, and the temperature of the bearing gas having an increased temperature existing in the journal bearing gap 13 is increased. It is often discharged toward the area facing the end of the sleeve, and the temperature rise is mitigated. As a result, the malfunction of the gas bearing spindle 1 due to the above-described thermal expansion can be avoided.

  In the first and second embodiments, the case where the nozzles are formed in two rows and three rows has been described as an example of the gas bearing spindle of the present invention. However, the gas bearing spindle of the present invention is not limited to this. The nozzles may be formed so as to form four or more rows. In the first embodiment and the second embodiment, a case where a total of two grooves are formed on each of the end face side and the side face side of the holding ring and an O-ring as an elastic member is fitted is described. However, for the purpose of improving airtightness, three or more grooves may be formed, and three or more elastic members may be fitted. Conversely, for the purpose of reducing the rigidity of the elastic member, etc., one elastic member is provided for each holding ring, and the functions of the elastic member for journal bearing and the elastic member for thrust bearing are the functions of the one elastic member. You may make it the structure which can be shared by an elastic member (for example, O-ring). Further, in the first and second embodiments, the description has been given of the mode in which the integral holding ring is fitted into each end of the sleeve as an example of the holding ring. For example, each holding ring is provided on the end side of the sleeve. It may be divided into a holding ring and a holding ring on the side surface side.

  The embodiment disclosed this time is to be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  The gas bearing spindle of the present invention can be applied particularly advantageously to a gas bearing spindle used in precision processing machines, hole processing machines, electrostatic coating machines and the like.

2 is a schematic cross-sectional view of a gas bearing spindle according to Embodiment 1. FIG. 6 is a schematic cross-sectional view of a gas bearing spindle according to Embodiment 2. FIG. It is a general | schematic fragmentary sectional view which shows an example of the conventional gas bearing spindle.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Gas bearing spindle, 10 Rotating shaft, 11 Shaft part, 11A Outer peripheral surface, 12 Flange part, 12A Bottom face, 12B Thin part, 13 Journal bearing gap, 14 Thrust bearing gap, 15 Turbine blade, 19 Holding part, 20 Housing, 21 Gas supply path for bearing, 22 annular space, 30 sleeve, 31 bearing portion, 32 retaining ring, 32A groove, 33 sleeve through hole, 41, 42 O-ring, 51 journal nozzle, 51C central journal nozzle, 52 sleeve air supply path, 60 gas thrust bearing, 61 thrust nozzle, 62 thrust bearing air supply path, 71 driving gas supply path, 72 circumferential groove, 73 turbine nozzle, 75 driving gas discharge path.

Claims (6)

A rotation axis;
A sleeve having a sleeve through hole which is a cylindrical through hole surrounding at least a part of the outer peripheral surface of the rotating shaft;
A housing that surrounds the sleeve and holds the sleeve via an elastic member;
The sleeve is
Non-metallic sintering having the sleeve through-hole, a part of the outer peripheral surface forming the outer peripheral surface of the sleeve, and the inner peripheral surface of the sleeve through-hole facing the outer peripheral surface of the rotating shaft A body bearing portion;
A gas holding ring that is fitted in each of both end portions of the bearing portion in the direction in which the sleeve through-hole extends and holds the sleeve against the housing via the elastic member. Bearing spindle.   The gas bearing spindle according to claim 1, wherein an annular groove extending in a direction along an outer periphery of the holding ring for holding the elastic member is formed in the holding ring. In the sleeve, a plurality of nozzles for supplying gas to a bearing gap provided between the inner peripheral surface of the sleeve through hole and the outer peripheral surface of the rotary shaft are formed on the peripheral wall of the sleeve,
3. The gas bearing spindle according to claim 1, wherein the nozzle is arranged so as to constitute a plurality of rows extending in a circumferential direction of the sleeve through-hole.   4. The gas bearing spindle according to claim 3, wherein the nozzles are formed in at least one or more rows on both sides sandwiching a central portion of the sleeve in a direction in which the sleeve through hole extends. 5.   In the direction in which the sleeve through-hole extends, the end nozzles located at both ends of the plurality of nozzles have a distance from the nearest one of the end portions on both sides of the sleeve of the length of the sleeve. 5. The gas bearing spindle according to claim 3, wherein the gas bearing spindle is formed at a position equal to or less than%.   The at least one said nozzle is formed in the position where the distance from the center part of the said sleeve is 20% or less of the length of the said sleeve in the extending direction of the said sleeve through-hole. The gas bearing spindle according to claim 1.

Images